Vancouver Canucks' Shane O'Brien reacts after scoring against the Chicago Blackhawks during the second period in Game 6 of the NHL Western Conference semifinal hockey series in Chicago, Monday, May 11, 2009. (AP Photo/Nam Y. Huh) (Nam Y. Huh)

Vancouver Canucks' Shane O'Brien reacts after scoring against the Chicago Blackhawks during the second period in Game 6 of the NHL Western Conference semifinal hockey series in Chicago, Monday, May 11, 2009. (AP Photo/Nam Y. Huh)(Nam Y. Huh)

Vancouver Canucks defenceman Shane O'Brien was missing from practice on Monday, and head coach Alain Vigneault refused to explain his absence.

"I'm not going to answer any questions on O'Brien today," a seemingly miffed Vigneault said during his daily press briefing.

Vigneault said O'Brien would not dress for a home game Tuesday against the Phoenix Coyotes. He said Andrew Alberts would take his place.

A published report said that O'Brien may have slept-in, but was spotted at GM Place on Monday. His agent, Ottawa-based Larry Kelly, did not return messages seeking comment.

O'Brien, 26, played more than 14 minutes on Saturday, in a 4-2 loss to San Jose, and had regained his regular spot in the lineup of late after being a healthy scratch earlier this season.

He crossed the organization last year when he said general manager Mike Gillis instructed him to fight in a series of one-on-one meetings with players. Gillis denied the accusation.

Forward Pavol Demitra was also absent from practice on Monday. He took leave from the team last week to tend to a personal matter.

But Vigneault wouldn't disclose whether O'Brien was also tending to personal business, or having a "maintenance day," the club's euphemism when it gives a player the day off. A team spokesman would not comment when asked if O'Brien was excused from practice.

Meanwhile, winger Mikael Samuelsson returned to practice on Monday, and is nearing a return from an upper-body injury. Samuelsson will travel with the team to California later this week, but Vigneault said it was too optimistic to project a return either Thursday (in Los Angeles) or Friday (in Anaheim). He could return Sunday, when the Canucks play host to the Minnesota Wild.